JPH0221522B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improved method for detecting and measuring printed marks.

Conventionally, the first method was to measure by detecting marks marked on the surface of a continuously moving object to be measured.
There are methods as shown in FIG. However, each of these has the following drawbacks.

In the method shown in FIG. 1, a mark detector 12 and a marking device 11 are arranged at a constant distance l,
In this method, the mark printed in step 1 is detected by a detector 12, and the device 11 is controlled in synchronization with the detection to print the next mark.

According to this method, marks are printed on the object to be measured 14 at intervals equal to the distance l between the device 11 and the detector 12, so if the counter 13 counts the number of times the object is detected by the detector 12, the object is moved. Distance can be easily measured. However, in reality, even if the device 11 is controlled by the detection signal without time delay, when marks are printed without contact using an inkjet method, the mark printing time is delayed by the flight time of the ink particles. , object to be measured 14
The interval between the marks printed on it becomes longer than l.

In order to reduce this error, l can be made large, but in such a case, the length measurement unit becomes very large, and there is a drawback that arbitrary lengths in short units cannot be measured.

The method shown in FIG. 2 is a method in which marks printed at a fixed time interval T are detected by two mark detectors 221 and 222 arranged a fixed distance l apart.

According to this method, the total moving distance can be accurately determined by counting the number of detected marks. However, in this method, if the interval between the marks printed is smaller than the length l between the two detectors 221 and 222, two or more marks will be placed between the detectors, so the two detectors will not be able to detect the mark. There is no guarantee that the marks used are the same, and it becomes impossible to measure the correct speed from the detection time difference. In addition, in this method, marks are printed at regular intervals, so the object to be measured 24
If the moving speed of the mark fluctuates significantly, the distance between the marks may change, making measurement impossible.

The present invention has been made with the object of providing an improved measuring method that eliminates the drawbacks of the conventional method described above and enables highly accurate measuring over a wide range of variation in the moving speed of an object to be measured. This will be explained below with reference to the drawings.

FIG. 3 shows the basic configuration of this invention.

The marking device 31 is started by a start signal from 39 to mark a mark on the object to be measured 34, and the marking time interval measuring device 36 is started. This measuring device 36 is composed of, for example, a counter that starts counting clocks in response to a start signal.

The marked mark moves together with the object to be measured 34 and is detected by the detector 321 at time _T1 ,
The mark detection time difference measuring device 35 is activated by the signal.

The mark moves further, and at time T ₂ when the mark reaches directly below the detector 322, a mark signal is detected by the detector, and this signal activates the marking device 31 to mark the next mark and measure the time difference. The counter 35 stops counting, the time difference τ between T ₁ and T ₂ is measured, and at the same time the contents of the counter of the time interval measuring device 36 are transferred to the buffer register 37, the contents are reset, and the next Start counting. By this method, the time intervals T of marks intermittently printed on the buffer register 37 are memorized.

The mark detection time difference τ held in the time difference measuring device 35 until the next mark is detected by the detector 321 and the marking time interval T held in the buffer register 37 are sent to the moving distance calculator 38. The moving distance between the marks is calculated by calculating l×T/τ, where l is the distance between the detectors 321 and 322.

This calculation is repeated each time a mark is detected by the second detection 322, and by integrating these calculations, the entire moving distance can be measured.

According to this method, marking is performed when the previous mark reaches directly below the second detector 322, so it is possible to make markings at constant intervals regardless of the moving speed of the object to be measured 34. It is.

That is, the distance between the marks will never become shorter than the distance between the two detectors 321 and 322, and the distance between the marks will never become shorter than the distance between the two detectors 321 and 322, and the distance between the marks will never become shorter than the distance between the two detectors 321 and 322. detector 3
21, 322 and the marking device 31 can be set at approximately constant intervals determined by the distance between the marking device 31 and the marking device.

FIG. 4 shows another example of the invention.

In response to a start signal from 49, a mark is first marked on the surface of the object to be measured 44 by the marking device 41, and movement is started. This mark is the first
5, a mark detection signal as shown in FIG. 5A is obtained, which activates the second time difference measuring device 452.

When the mark moves further and reaches directly below the second detector 422, this detector 422 obtains the signal shown in FIG. Time difference (τ)
Measure. At the same time, the first time difference measuring device 451 is activated and the marking device 41 is activated to perform marking, and the mark detection frequency counter 43 counts the number of mark detections.

The next mark marked is the first detector 421
is detected by the first measuring device 4 based on the detection signal.
51 is stopped. As a result, the time ΔT from activation of the device 41 to arrival of the next mark is measured, and at the same time, the second measuring device 452 is activated.

By repeating the above operations, the time difference ΔT from the activation of the device 41 to the detection of the marked mark by the first detector 421 is further increased.
The time difference τ until the mark is detected by the second detector 422 is sequentially measured, and the number N of times the mark is detected by the second detector 422 is counted by the counter 43. If it is possible to mark the mark on the object to be measured 44 without any time delay by starting the device 41, the corresponding moving distance will be the distance l between the two detectors, regardless of the time difference between the two detectors. is equal to the distance l' between the first detector 421 and the device 41, so the product N(l+
l′) should be the distance traveled.

However, in reality, there is a delay from the start of the device 41 until the mark is printed, so the object to be measured 44 moves during that time, and the value of l' depends on the speed of the object to be measured 44 and changes in speed. It will change. Therefore, in order to measure the correct moving distance, the period between the period during which the mark moves between the two detectors 421 and 422 and the period from when it is marked until it is detected by the first detector 421 is determined. Based on the assumption that there is no speed change, from the time ratio of τ and △T,
l′=l×△T/τ, and the mark printed by the marking device 41 is transferred to the second detector 42.
2, the distance traveled until it is detected is l(1+△T/τ)
By calculating as follows, it becomes possible to measure the moving distance more accurately.

However, even with this method, the following measurement errors may occur if the speed changes quickly.
As shown by the solid line in FIG. 6, when the speed changes with time, that is, the (n-1)th mark is detected by the first detector 421 at point o and passes through a.
The n-1th mark at point b is the second detector 422
The time difference between them is τn-1 and the distance is l.

Here, the device 41 is activated, and until the n-th mark is detected by the first detector 421, △
Assume that time Tn has passed and the robot moves to point C.

However, if we calculate the travel distance by assuming that we moved at the same speed as from point o to point b during this period of △Tn, the reached point will be regarded as point C′, and △
This results in an error of l′.

One of the objects of the present invention is to provide a method for significantly reducing the error even in such a case. The method will be explained below.

It is impossible to directly know the average speed during the period ΔTn from starting the device 41 as described above until the mark is detected by the first detector 421. However, before and after the period ΔTn, the n-1 and nth marks are detected by the first detector 421.
Since the mark passes a certain distance l during the periods τn-1 and τn until it passes directly under the second detector 422 and reaches directly below the second detector 422, it is possible to know the correct speed.

Therefore, by considering the speed during the period △Tn to be equal to the average value of the speeds during the two periods τn-1 and τn narrowing this period, and calculating the moving distance during the period △Tn, the error can be reduced. can be significantly reduced.

To explain this using Fig. 6, if the average speed during the period △Tn is equal to the period τn-1, the distance reached at the end of the period △Tn is C',
Also, if the speed is equal to the speed of the τn period, it becomes C'', which results in large errors as shown in △l' and △l'', respectively, but by taking the average of these, △
It is shown that the reach distance at the end of the period Tn takes a value between C' and C'', which almost matches the correct reach distance C. Expressing this in a formula, the n-1th mark and The distance L(n-1, n) from the nth mark is expressed as L(n-1, n)=l+l/2△Tn (1/τn-1+1/τn), where n2 .

After the start of measurement, the nth mark is the second detector 42
The total moving distance of the object to be measured until it reaches the position directly below the point 2 is calculated by the integrated value of L(n-1, n) and the distance l until the first marking mark is detected by the first detector 421. ' (which is equal to the distance between device 41 and detector 421) plus the distance l traveled by the Nth mark between the two detectors. Therefore, the total moving distance L is expressed by the following equation.

L=[N+1/2 ₁ 〓 ⁿ⁼² △Tn (1/τn-1+1/τn)]×l In other words, the time widths τn-1, τn and n during which two adjacent marks pass through two detectors respectively - Sequentially measure the time difference ΔTn from when the first mark is detected by the second detector 422 to when the nth mark is detected by the first detector 421, and By counting the number of mark detections N, even if the moving speed of the object to be measured varies, the moving distance can be calculated and measured with high accuracy. The measurement of τn-1, τn and ΔTn is carried out using the mark detection time difference measuring devices 451 and 452 shown in FIG.
For example, the mark detection signal from 22 operates a flip-flop that can be set and reset, and generates gate pulses corresponding to periods of τn and △Tn as shown in C and E, thereby causing constant pulses as shown in D and F. This can be done by counting the periodic clocks. These measurement results are sent to 48 moving distance calculators, and the moving distance is calculated according to the above-mentioned formula.

[Brief explanation of drawings]

1 and 2 are explanatory diagrams showing an example of a conventional measuring method, respectively, FIGS. 3 and 4 are explanatory diagrams respectively showing an example of a measuring method according to the present invention, and FIG. FIG. 6 is a diagram explaining the principle of mark detection time difference detection in the example shown, and FIG. 6 is a diagram explaining measurement accuracy in the example shown in FIG. 31, 41...Marking device, 321, 32
2,421 and 422...mark detector, 43...mark detection number counter, 44...object to be measured, 3
5,451 and 452... mark detection time difference measuring device, 36... marking time interval measuring device, 37... buffer register, 38 and 48... moving distance calculator.

Claims (1)

[Claims] 1. A marking device and a mark detector are arranged along the moving direction of an object to be measured that moves continuously in a certain direction, and the mark marked on the object to be measured by the marking device is detected by the mark detector. In this method, two mark detectors are placed at a certain distance downstream of the marking device, and one of the mark detectors is placed downstream of the marking device. The marking device is controlled based on the signal from the arranged mark detector to mark a mark on the object to be measured, and from the time when the marking device is activated, the mark marked thereby is detected as a mark on the upstream side. The time period until the mark is detected by the mark detector is measured by a time measuring device that operates based on the mark detection signal from the mark detector, and the distance traveled by the object to be measured during the period is calculated by measuring the distance between the two mark detectors. It is calculated as the average value of the measured value of the moving speed and the measured value of the speed of the previous mark moving between the two mark detectors, and the calculated value is calculated as the average value of the measured value of the moving speed of the previous mark A measuring method for a continuously moving object, characterized in that the moving distance of the object to be measured is calculated by adding it to a fixed amount of movement between instruments.